Allozyme analysis of tissue samples of 910 European hake Merluccius merluccius from six North Atlantic Ocean and four Mediterranean Sea locations revealed polymorphism at 21 out of 34 protein-coding loci examined. A major subdivision between Atlantic and Mediterranean collections (mean Nei's genetic distance within regions 0.005; between regions 0.014) was particularly evident from allelic differences at the GAPDH-1* and GR-2* loci. Further population subdivision was indicated within both regions, and gene flow from adjacent Atlantic to proximal Mediterranean populations was suggested by allele frequencies and relevant oceanographic and geological information. The data support present management based on distinct Atlantic and Mediterranean populations and indicate that the population structure within the Atlantic is more complex than the discrete northern and southern stocks proposed by ICES.

Genetic data from nine species of Merluccius (Euro±African species merluccius, capensis, paradoxus, polli, senegalensis; American species bilinearis, productus, hubbsi, australis) from 21 informative allozyme loci provided insights into the phylogenetic and biogeographical relationships within the genus. The highest values of polymorphic loci and mean heterozygosity occur in the four American species. These values are consistent with large population sizes during speciation (through vicariant processes), and continuing through to the present. Conversely, the lower values of Euro±African species are consistent with bottlenecks occurring during or subsequent to speciation. Euro±African and American species formed two distinct clades. In the former group, merluccius, capensis and senegalensis clustered together as the most derived species, with distinct relationships between polli and paradoxus from an earlier divergence. Similarly, productus, australis and hubbsi clustered closely as the most derived American species, clearly diverging from the more ancestral bilinearis. Analyses including comparative data previously published for M. gayi indicated a close pairing to hubbsi. The data support a north-west Atlantic origin of the genus with unsampled M. albidus of broad Caribbean distribution proposed as the most primitive extant species.Keywords: allozymes, biogeography, hake, Merluccius, phylogeny. IntroductionThe genus Merluccius (Ra®nesque) (Gadiformes: Merlucciidae) has a broad latitudinal distribution in the Atlantic and Paci®c Oceans. In the most complete revision on the genus, Inada (1981) recognized 12 species (Table 1). The existence of an additional species, M. hernandezi from the Gulf of California, has also been indicated but its taxonomic status is uncertain (Cohen et al., 1990). The degrees of divergence, phylogenetic relationships and biogeography within Merluccius have generated considerable speculation (Szidat, 1955; Inada, 1981; Kabata & Ho, 1981).Two major hypotheses for the origin and dispersal of Merluccius agree that hakes originated in the Atlantic and entered the Paci®c through the then-open Panamanian seaway. They di er, however, in details of the origins of the Argentine hake M. hubbsi. A proposed eastern origin of M. hubbsi from a South Paci®c stock that rounded Cape Horn to reach Argentina (Szidat, 1955; Inada, 1981) contrasts with a postulated derivation from a western North Atlantic stock (Kabata & Ho, 1981; Ho, 1990).The morphological similarities among species and the uncertainty of phylogenetic relationships, suggest the application of molecular techniques. These methods have provided critical insights towards resolving similar problems in other teleost taxa. Estimated divergence among ®sh taxa, traditionally based on morphological measurements, may mask true genetic relationships, which are more precisely re¯ected by molecular genetic data (Grant, 1987). Allozyme electrophoresis has been a widely applied molecular method for comparing levels of genetic divergence between taxa (...

The blue and red shrimp Aristeus antenantus supports an important commercial fishery in the Western Mediterranean, adjacent Atlantic waters and Mozambique Channel (western Indian Ocean). This study investigates its genetic structure by examining a total of 506 individuals from Mediterranean, Atlantic and Indian Ocean locations. In order to identify putative genetic stocks, sequences from 16S rDNA (546 bp) and COI (514 bp) genes were used. Genetic diversity, estimated by haplotypic and nucleotidic diversity, was lower in the Western Mediterranean than in samples from other locations. The high haplotypic diversity of the Eastern Mediterranean, Atlantic and Indian Ocean samples reflects the occurrence of a number of private haplotypes, which are also responsible for significant genetic divergence between these samples and the Western Mediterranean ones. The analysis of mismatch distributions, neutrality tests, and star-like patterns present in the network of haplotypes provided consistent inference of past population expansion in the Western Mediterranean, Atlantic and Mozambique Channel regions. Our study provides the first evidence of genetic structuring in A. antennatus across its distributional range.KEY WORDS: Aristeus antennatus · COI · 16S rDNA · Genetic structure · Atlantic Ocean · Mediterranean Sea · Western Indian Ocean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 421: [163][164][165][166][167][168][169][170][171] 2011 roboration of Atlantic-Mediterranean differentiation has been provided by multiple examples of the population structure of marine species, from pioneer work on crustaceans (Chthamalus montagui, Dando & Southward 1981), mollusks (Mytilus galloprovincialis, Quesada et al. 1995a,b; Sepia officinalis, Pérez-Losada et al. 1999) and fishes (Platichthys flesus, Borsa et al. 1997; Merluccius merluccius, Roldán et al. 1998) down to the present day.The blue and red shrimp Aristeus antennatus (Risso, 1816) is an important commercial deep-sea species that inhabits the Mediterranean, northeast Atlantic waters from Portugal to the Cape Verde Islands (Holthuis 1980), and the Indian Ocean from the Maldive Islands to Zanzibar, Mozambique and South Africa (Freitas 1985). In recent years, it has also been recorded off the northern coasts of Brazil (Serejo et al. 2007). A. antennatus is a eurybathic species ranging from 80 to 3300 m depth, with peaks of abundance at 600 to 900 m depth (Campillo 1994, Sardà et al. 2004). Its abundance is also geographically variable, with density in the Western Mediterranean being higher than that in the eastern basin ). Significant morphological differences have been observed in individuals from the 2 basins. However, no allozyme divergence was found (Sardà et al. 1998) and the differences were explained as being a response to hydrological and ecological characteristics of the 2 Mediterranean basins (Sarà 1985). Recently, new molecular markers (microsatellites, Cannas et al. 2008; mitochondrial control region, ...

Systematics derived from morphological characters often does not correspond with the evolutionary processes underlying the divergence within a group of organisms. In the family Mugilidae (Teleostei) morphological similarities have resulted in inconsistencies between taxonomy and phylogeny among its species, and particularly for the genera Mugil, Liza and Chelon where both intrageneric and intergeneric phylogenetic clarifications are needed.

In this paper we addressed the phylogeographical genetic structure of the economically important red shrimp, Aristeus antennatus (Crustacea, Aristeidae) in the Western Mediterranean. Partial mitochondrial regions of the cytochrome c oxidase subunit I (514 bp) and ribosomal 16S subunit (547 bp) were sequenced in 137 individuals collected at three localities: Catalan Sea, Ligurian Sea and the southern Tyrrhenian Sea. Values of haplotypic diversity were h = 0.552-0.724, whereas those for nucleotide diversity were pi = 0.0012-0.0026. Among-sample genetic diversity was not significant and no geographical patterns in the distribution of haplotypes were apparent. Results of the present study are consistent with a past population expansion that occurred <2,000 years ago. Despite the current fishing pressure, genetic variability appears to be sufficiently high to keep A. antennatus populations stable over time. Dispersal-related life history traits may account for the shallow genetic structure. Our results are not in contrast with the hypothesis of sustainability of Western Mediterranean red shrimp fisheries predicted on the basis of previously obtained biological results.

The mechanisms of competition and resource domination were analysed in the Mediterranean ant Camponotus cruentatus. In a plot located in southern Spain mature colonies are overdispersed, which is indicative of territoriality in other species. Unexpectedly, however, workers from neighbouring colonies commonly foraged in areas that overlapped by more than 44%. This suggests that while mature colonies possibly prevent the establishment of new colonies in the vicinity of their nests, they do not limit the intrusion of alien foragers. In contrast, rich food sources located in common foraging areas are aggressively defended, generally leading to their domination by the nest that discovered them first. Resource exploitation further requires rapid recruitment of foragers and soldiers to transport food as well as to exclude competitors. Complementary to the field experiments we conducted laboratory bioassays to assess intercolonial aggression. Group encounters showed that workers of C. cruentatus were equally aggressive towards alien ants irrespective of whether they were sympatric neighbours (and had possibly had contact), sympatric nonneighbours (which had probably had no contact), or allopatric. This was corroborated by analysis of the hydrocarbons that generally serve as colony recognition cues. This mixture, which contains an unusual proportion of trimethylalkanes, showed important colony specificity. The high intraspecific aggression shown indiscriminately by workers indicates that the 'dear enemy' effect does not exist in this species and suggests that scarce resources are worth defending against intraspecific competitors. We discuss several proximate and ultimate constraints that may prevent the general occurrence of this process in ants.

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